View Full Version : How does dry time effect emulsions?

01-22-2010, 06:19 PM
Last August 8 I made some notes from APUG and it was a good thing that I did because I can't find the source now.

The article or post said that Dry time is a factor according to Mark S. Pederson, a writer in APUG (can't find him either). The notes say that 24 hours drying time (of Liquid Light I think) gives a ASO of 1/4, 48 - 72 hours drying gives ISO 1/2, 5 days or more ISO of 1, and 14 days will fog emulsion.

Where is that post?

The reason is that I made a 4x5 plate and exposed it and got a picture. Howeve, the exposure was way longer than others under similar conditions, namely bright sun. The difference was that the new long exposure was cooked dry in the oven for over one hour, not dried one or two days in a cool dark room.

01-22-2010, 08:07 PM
Personaly, I never make conclusions by comparing one print to one print. Or even one print to many. But if you heated a print befor it was dry, probably the viscosity plunged down and the coating spread out and formed a thiner layer of emulsion. Then you are comparing different thicknesses, There very well could be a reduction in ISO for "older" dried plates. But you would have to treat them identicly, except for aging, to make that conclusion.